1. Field of the Invention
This invention relates generally to microscale devices for performing analytical testing and, in particular, to a valve for use in laminated plastic microfluidic structures.
2. Description of the Prior Art
Microfluidic devices have recently become popular for performing analytical testing. Using tools developed by the semiconductor industry to miniaturize electronics, it has become possible to fabricate intricate fluid systems which can be inexpensively mass produced. Systems have been developed to perform a variety of analytical techniques for the acquisition of information for the medical field.
Microfluidic devices may be constructed in a multi-layer laminated structure where each layer has channels and structures fabricated from a laminate material to form microscale voids or channels where fluids flow. A microscale channel is generally defined as a fluid passage which has at least one internal cross-sectional dimension that is less than 500 xcexcm and typically between about 0.1 xcexcm and about 500 xcexcm. The control and pumping of fluids through these channels is affected by either external pressurized fluid forced into the laminate, or by structures located within the laminate.
Many different types of valves for use in controlling fluids in microscale devices have been developed. U.S. Pat. No. 4,895,500, which issued on Jan. 23, 1990, describes a silicon micromechanical non-reverse valve which consists of a cantilever beam extending over a cavity and integrally formed with the silicon wafer such that the beam can be shifted to control flow within channels of the microfluidic structure.
U.S. Pat. No. 5,443,890, which issued Aug. 22, 1995 to Pharmacia Biosensor AB, describes a sealing device in a microfluidic channel assembly having first and second flat surface members which when pressed against each other define at least part of a microfluidic channel system between them.
U.S. Pat. No. 5,593,130, which issued on Jan. 14, 1997 to Pharmacia Biosensor AB, describes a valve for use in microfluidic structures in which the material fatigue of the flexible valve membrane and the valve seat is minimized by a two-step seat construction and the fact that both the membrane and the seat are constructed from elastic material.
U.S. Pat. No. 5,932,799, which issued Aug. 3, 1999 to YSI Incorporated, teaches a microfluidic analyzer module having a plurality of channel forming laminate layers which are directly bonded together without adhesives, with a valve containing layer directly adhesivelessly bonded over the channel containing layers and a flexible valve member integral with the valve layer to open and close communication between feed and sensor channels of the network.
U.S. Pat. No. 5,962,081, which issued Oct. 5, 1999 to Pharmacia Biotech AB, describes a method for the manufacturer of polymer membrane-containing microstructures such as valves by combining polymer spin deposition methods with semiconductor manufacturing techniques.
U.S. Pat. No. 5,971,355, which issued on Oct. 26, 1999 to Xerox Corporation, describes a valve array system for microdevices based on microelectro mechanical systems (MEMS) technology consisting of a dielectric material forming a laminate which is embedded within multiple laminate layers.
U.S. Pat. No. 6,068,751, which issued on May 30, 2000, describes a microfluidic delivery system using elongated capillaries that are enclosed along one surface by a layer of malleable material which is shifted by a valve having a electrically-powered actuator.
U.S. patent application Ser. No. 09/677,250, filed on Oct. 2, 2000, now U.S. Pat. No. 6,431,212, and assigned to the assignee of the present invention describes a one way check valve for use in laminated plastic microfluidic structures. This valve allows one way flow through microfluidic channels for use in mixing, dilution, particulate suspension and other techniques necessary for flow control in analytical devices.
Several types of valves are commonly used for fluid management in flow systems. Flap valves, ball-in-socket valves, and tapered wedge valves are a few of the valve types existing in the macroscale domain of fluid control. However, in the microscale field, where flow channels are often the size of a human hair (approximately 100 microns in diameter), there are special needs and uses for valves which are unique to microscale systems, especially microfluidic devices incorporating fluids with various concentrations of particulate in suspension. Special challenges involve mixing, dilution, fluidic circuit isolation, and anti-sediment techniques when employing microscale channels within a device. The incorporation of a simple compact valve within microscale devices addresses these potential problems while maintaining high density of fluidic structure within the device.
It is therefore an object of the present invention to provide an efficient and reliable valve suitable for use in a microfluidic system.
It is a further object of the present invention is to provide a microfluidic valve which can be integrated into a cartridge constructed of multi-layer laminates.
It is a further object of the present invention is to provide an array of microfluidic valves that can be integrated into a cartridge constructed of multilayer laminates.